The present invention is an improvement over couplings for flexible tubes used as fluid conduits in many different fluid power systems such as, for example, tubes for conveying pressurized air in vehicle air brake systems and air conditioning systems. The tubes require a coupling to connect the end of the tube to a body which may be a conventional fitting, valve, manifold, or similar device for transmitting and receiving pressurized air. Connecting a tube to a body, or removing the tube from a body, can be a time consuming and expensive task which is frequently performed in the field where specialized tools may not be readily available.
There are a wide variety of "push-to-connect" type couplings which permit a tube to be quickly and easily connected to a body without the use of tools. With these couplings, the tube is connected by simply press fitting the coupling in a bore within the body and then inserting the leading end of the tube into the coupling. Typically, the coupling contains a plurality of components which releasably retain the tube therein.
In order for presently used couplings to perform effectively, the bores in the bodies to which the tubes are connected are stepped and formed with relatively tight tolerances. In order to reduce manufacturing expenses and lessen the occurrences of coupling malfunctions, it is preferable to have unstepped bores which can be made with higher tolerances. Since currently available couplings require stepped bores, there is a need for new quick connect tube couplings which function effectively with an unstepped bore configuration.